TWI468223B - Modified trilobe shape for maleic anhydride catalyst and process for preparing maleic anhydride - Google Patents

Description

Improved three-lobed maleic anhydride catalyst and method for producing maleic anhydride

The present invention relates generally to a process for the preparation of maleic anhydride, and more particularly to a shaped catalyst structure useful for the preparation of maleic anhydride comprising a catalytic material comprised of a composite oxide of vanadium and phosphorus.

Various vanadium-containing and phosphorus-containing catalysts used in the preparation of maleic anhydride from butane have been described in the literature. Catalyst ingots of various shapes for the preparation of maleic anhydride are described, for example, in U.S. Patent Nos. 4,283,307 and 5,168,090.

One disadvantage of current tablet-type catalysts is that they have relatively low side crush strength. The side crush strength is a measure of the weight or strength required to break the tablet catalyst. The side crush strength is important in the manufacture of catalysts because it directly affects the durability of the catalyst during handling, transportation, and installation into a commercial reactor. In the case where all other factors are consistent, a catalyst having a higher crushing strength is preferred than a catalyst having a lower crushing strength.

Another disadvantage of current tablet-type catalysts is that they have a relatively high percentage loss. Percentage loss is an indicator of the amount of catalyst that is damaged by cracking after a certain loss and crack (see below). Percentage loss is important in the manufacture of catalysts because it directly affects the durability of the catalyst during handling, transportation, and installation into a commercial reactor. Catalysts with lower percentage wear are more stable than catalysts with higher percentage wear, all other factors are consistent.

Catalyst ingots with lower side crush strength and higher percentage loss tend to produce more broken catalyst tablets and more catalyst fines during handling, transportation, and installation into a commercial reactor. These broken catalyst pellets and catalyst fines can cause an increased pressure drop in a properly functioning commercial reactor tube and are therefore undesirable.

Embodiments of the present invention disclose shaped oxide catalyst structures for the preparation of maleic anhydride. The shaped structure contains a catalytic material composed of a mixed oxide of vanadium and phosphorus. The formed structure has a solid cylindrical structure in which the cylindrical structure has a cylinder height and a cylindrical radius. The solid cylindrical structure has three void spaces that travel along the height of the cylinder to form three lobes. Each flap has a corner defined by the radius of the flap. For this type of structure, the ratio of the radius of the cylinder to the radius of the lobes is equal to or less than about 15.

Embodiments of the invention include a method of preparing maleic anhydride. In the presence of the shaped oxidation catalyst structure of the present invention, a hydrocarbon having at least four carbon atoms in the linear chain is reacted with a gas containing molecular oxygen.

Embodiments of the present invention include maleic anhydride which is a method of reacting a hydrocarbon having at least four carbon atoms in a linear chain with a gas containing molecular oxygen in the presence of the shaped oxidation catalyst structure of the present invention. preparation.

The features of the present invention are broadly described in order to provide a better understanding of the invention. Additional features and advantages of the invention will be set forth hereinafter, which form the subject of the scope of the invention. Those skilled in the art will appreciate that the concept and disclosure of specific embodiments can be used as a basis for improving or designing other structures for the same purposes as the present invention. It is also understood by those skilled in the art that these equivalent constructions are not to be construed as limited by the scope of the invention.

Therefore, for a more detailed understanding of the aspects of the present invention as described hereinbelow, It is to be understood, however, that the appended claims The units of measure in these drawings are inches.

1A, 1B, 1C and 3A show the current three-lobed tablet. The three-lobed ingot is a solid cylindrical structure having a height "h" (Fig. 1A) and a radius "r" (Fig. 1B). This solid cylindrical structure has a void space that travels along the height of the cylinder to form three lobes L1, L2, and L3 (Fig. 1B). Each flap has a corner whose shape is defined by the lobes radius "Lr" (0.0080 inches in Figure 1C).

It has been unexpectedly discovered that if the radius of the flap of the three-lobed tablet is extended such that the ratio of the radius of the cylinder to the radius of the flap is equal to or less than about 15, the lateral crushing strength of the catalyst can be improved to a lower percentage. Loss and better packing density (and thus improved catalyst performance). The term "improved catalyst performance" means that at least one catalyst property is improved, including yield, selectivity, conversion, yield over time, selectivity, conversion performance, load characteristics, and operability. These results are not expected in previous teachings on catalyst structures. That is, those skilled in the art will anticipate that prolonging the flap radius will result in approximately equivalent comminution strength and percent wear and may have a negative impact on the catalyst performance of such catalysts due to a reduction in surface area.

An embodiment of the invention is illustrated in FIG. Figure 2 shows a modified three-lobed tablet in which the radius of the flap has been extended. Figure 2 shows a modified three-lobed tablet with a modified flap radius (mLr) of 0.0200 inches, which is 2.5 times the original flap radius (Lr = 0.0080 inches) in Figure 1C. A comparison of two different lobes of curvature can be more clearly presented in Figures 3A and 3B. Extending the radius of the flap produces an improved three-lobed tablet with an open and smooth shape.

In an embodiment of the invention, the ratio of the radius of the cylinder to the radius of the lobes is equal to or less than about 15. In other embodiments, the ratio is equal to or less than about 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, or 3. In another embodiment, the ratio is about 6.25. Appropriate proportions that can be used in embodiments of the invention will be understood from the benefit of this disclosure.

Embodiments of the invention include a molded structure that consumes less than about 10%. In other embodiments, the molded structure has a loss of less than about 11%, 12%, 13%, 14%, or 15%. The measurement of wear and tear is detailed in the example paragraph.

Embodiments of the invention include a formed structure having a side crush strength greater than about 10 pounds. In other embodiments, the side crush strength of the formed structure is greater than about 15, 16, 17, 18, 19, or 20 pounds. The measurement technique of the side crush strength is described in the example paragraph.

The molded structure of the embodiment of the present invention contains a catalyst material composed of a mixed oxide of vanadium and phosphorus. Catalytic materials for use in the present invention are known in the art and are generally those materials which can partially oxidize a hydrocarbon vapor phase to maleic anhydride under oxidizing conditions. Such materials generally include a vanadium phosphorus oxide complex, optionally including a promoter element. Although not limited, suitable catalyst materials can be represented by the formula: VP _x O _y M _z , wherein M is at least one promoter element selected from the group consisting of IA, IB, IIA, IIB, IIIA of the Periodic Table of the Elements a group of elements in the group IIIB, IVA, IVB, VA, VB, VIB or VIIIB, x being a value between about 0.5 and about 2.0, preferably between about 0.95 and about 1.35, and y being satisfied The value of the oxidized state of the V, P and M valences present in the composition, z is a value between 0 and about 1.0, preferably at most about 0.5. The term "periodic table of elements" as referred to herein means The Merck Index, 10th edition, Windholtz, Ed., Merck & Co., Inc., Rahway, NJ, 1983, the periodic table of elements of the inner cover page.

Although not limited, specific examples of suitable catalyst materials are described in U.S. Patent Nos. 4,632,915, 4,562,268, 4,333,853, 4,315,864, 4,312,787, 4,251,390, 4,187,235, 4,018,709, 3,980,585, 3,888,866, 3,864,280, 3,862,146 and 3,856,824, and European Patent Application No. 98,039 It should be understood that the same should not be construed as limiting, but rather to illustrate and guide the operation of the invention. The above references are incorporated herein by reference. Among these catalyst materials, the present invention is generally described in U.S. Patent Nos. 4,632,915, 4,562,268 and 5,275,996.

The shaped oxidation catalyst structure of the present invention can be prepared by blending a catalytic material with a molding structure forming aid known in the art such as graphite or stearic acid and any desired inert filler material, and in a mold (with a nozzle) And punching presses are compressed or compressed, or extruded or cast according to procedures known in the art. In general, compression techniques are preferred for forming structures that are more readily available to exhibit the characteristic properties of the present invention. In a similar process, the reaction to partially oxidize a hydrocarbon to maleic anhydride can advantageously be carried out in such a manner that a maximum amount of active catalyst material is contained in a particular volume of reactor, thereby allowing a single pass of carbon. In the case where the hydrogen compound is converted to the maximum amount, it is preferred not to use an inert filler material.

Embodiments of the invention disclose methods of preparing maleic anhydride. In one embodiment, the method of preparing maleic anhydride comprises the steps of reacting a hydrocarbon having at least four carbon atoms in a linear chain with a molecular oxygen-containing gas in the presence of a shaped oxidation catalyst structure, the catalyst The material consists of a mixed oxide of vanadium and phosphorus and is a solid cylindrical structure in which the cylindrical structure has a cylinder height and a cylinder radius, and the solid cylindrical structure has three voids along the cylinder height The space is formed into three lobes, wherein each lobes has a corner defined by the lobes radius, wherein the ratio of the radius of the cylinder to the radii of the lobes is equal to or less than about 15.

The shaped oxidation catalyst structure of the present invention can be used in various reactors to convert non-aromatic hydrocarbons to maleic anhydride. A typical satisfactory reactor is a tube-shell fixed bed (tube type) with a heat exchange type reactor. The details of the operation of such reactors are well known to those skilled in the art. The tubes of these reactors may be constructed of iron, stainless steel, carbon steel, nickel, glass (such as Vickers glass in the United States) and may range in diameter from about 0.635 cm (0.25 inches) to about 3.81 cm (1.50 inches), length. The range can vary from about 15.24 cm (6 inches) to about 762 cm (25 feet). The oxidation reaction is a highly exothermic reaction, and once the reaction begins, in order to maintain the desired reactor temperature, heat transfer medium must be used to conduct heat away from the reactor. Suitable heat transfer media are well known to those skilled in the art and are generally materials which are still liquid at the reaction temperature and which have a relatively high thermal conductivity. Examples of useful heat transfer media include various heat transfer oils, molten sulfur, mercury, molten lead, and salts such as alkali metal nitrates and nitrites. Among them, the salt is preferred because of its high boiling point. A particularly preferred heat transfer medium is a eutectic mixture of potassium nitrate, sodium nitrate and sodium nitrite which not only has the desired high boiling point, but also has a sufficiently low melting point to maintain a liquid state even when the reactor is closed. An additional method of controlling the temperature is to use a metal block reactor whereby the metal surrounding the reaction zone of the reactor acts as a temperature regulator or utilizes conventional heat exchangers.

Generally, the reaction of converting a non-aromatic hydrocarbon into maleic anhydride using the shaped oxidation catalyst structure of the present invention comprises the inclusion of a non-aromatic hydrocarbon having at least four carbon atoms in a linear (or cyclic structure) Molecular oxygen gas (including oxygen itself), such as a mixture of air or molecular oxygen-rich gas, is fed into a reactor or reaction zone cooled by a heat transfer medium filled with a shaped oxidation catalyst structure of the present invention to provide hydrocarbon The compound/molecular oxygen containing gas mixture is contacted with the catalyst at elevated temperatures. In addition to hydrocarbons and molecular oxygen, other gases such as nitrogen or steam may be present in the reactant feed stream or such other gases may be added. Generally, the hydrocarbon and the molecular oxygen-containing gas are preferably mixed with air at a concentration of from about 1 mol% to about 10 mol% of the hydrocarbon concentration, and the catalyst is at a gas space velocity (GHSV) or simple. a space velocity between about 5,000hr ^-1 to about 100hr ^-1 and a reaction temperature of from about 300 to about 600 deg.] C lower contact deg.] C, preferably at a space velocity of from about 1,000hr ^-1 to about 3,000hr ^-1 and a temperature of Contacting at about 325 ° C to about 450 ° C to obtain maleic anhydride.

However, the initial production of maleic anhydride may be lower. And if it is in such a situation, it will be apparent to those skilled in the art that the catalyst can be adjusted by forming the shaped oxidation catalyst structure of the present invention with a low concentration of carbon for a period of time prior to the start of the production run. The hydrogen compound and the molecular oxygen-containing gas are contacted at a low space velocity.

The pressure is not critical in the reaction to convert non-aromatic hydrocarbons to maleic anhydride. The reaction can be carried out under atmospheric pressure, super-atmospheric pressure or under reduced pressure. For practical reasons, however, it is generally preferred to carry out the reaction at atmospheric or near atmospheric conditions. Typically, at a pressure of between about 1.013 x 10 ² kPa-gauge (14.7 psig, 1 atm) to about 3.45 x 10 ² kPa-gauge (50.0 psig), preferably from about 1.24 x 10 ² A kPa-gauge pressure (18.0 psig) to about 2.068 x 10 ² kPa-gauge pressure (30.0 psig) can be suitably applied.

The maleic anhydride prepared using the shaped oxidic catalyst structure of the present invention can be recovered by any means known to those skilled in the art. For example, maleic anhydride can be recovered by direct condensation or by subsequent separation and purification of maleic anhydride by absorption in a suitable medium.

A large amount of non-aromatic hydrocarbons having 4 to 10 carbon atoms can be converted to maleic anhydride using the shaped oxidation catalyst structure of the present invention. It is only necessary to have a linear or cyclic structure of hydrocarbons of not less than 4 carbon atoms. For example, conversion of saturated hydrocarbon n-butane to maleic anhydride is satisfactory, but isobutane (2-methylpropane) is unsatisfactory, although its presence is not harmful. In addition to n-butane, other suitable saturated hydrocarbons include pentanes, hexanes, heptanes, octanes, decanes and decanes, and any mixtures thereof, with or without Butane, as long as the linear chain in the saturated hydrocarbon molecule has at least 4 carbon atoms.

The use of the shaped oxidic catalyst structure of the present invention is also suitable for converting unsaturated hydrocarbons to maleic anhydride. Suitable unsaturated hydrocarbons include butenes (1-butene and 2-butene), 1,3-butadiene, pentenes, hexenes, heptenes, octenes, terpenes And terpenes, and any mixtures thereof, with or without butenes, are again illustrated as long as the hydrocarbon molecules have at least 4 carbon atoms in a straight chain.

Using the shaped oxidizing catalyst structure of the present invention, cyclic hydrocarbons such as cyclopentane and cyclopentene are also satisfactory feed materials for conversion to maleic anhydride. Aromatic hydrocarbons such as benzene are satisfactory feed materials.

Among the above raw materials, n-butane is a preferred saturated hydrocarbon and butene is a preferred unsaturated hydrocarbon, and n-butane is the best among all the raw materials. Mixtures of the above materials are also satisfactory feed materials.

It should be noted that the above raw materials need not necessarily be pure substances, but may be technical grade hydrocarbons.

The most important product obtained by oxidizing the above suitable feed material is maleic anhydride, but when the starting material is a hydrocarbon having more than 4 carbon atoms, a small amount of citraconic anhydride (methyl maleic anhydride) is also produced.

The embodiment of the present invention also discloses maleic anhydride, which is obtained by reacting a hydrocarbon having at least 4 carbon atoms in a linear chain with a molecular oxygen-containing gas in the presence of a shaped oxidation catalyst structure, and the formed structure contains a catalyst material composed of a mixed oxide of vanadium and phosphorus, and having a solid cylindrical structure, wherein the cylindrical structure has a cylinder height and a cylinder radius, and the solid cylindrical structure has three cylinder heights The traversing void space is formed to form three lobes, wherein each lobes has a corner defined by the lobes radius, wherein the ratio of the cylinder radii to the lobes radius is equal to or less than about 15.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following is a description of specific examples of the presently preferred methods for applying the present invention so that the present invention can be clearly understood. It should be understood, however, that the description of the preferred embodiments of the invention may be Various changes and modifications are made without departing from the spirit of the invention.

Instance

The current three-lobed and modified three-lobed catalyst tablets were made from vanadium pyrophosphate powder in the following manner. The side crush strength and percent wear were measured for both tablet shapes.

A vanadium pyrophosphate catalyst powder is prepared according to a conventional method entitled "Phosphorus/Vanadium Oxide Catalyst and Process for Its Preparation" according to U.S. Patent No. 5,275,996. This powder was formed into a catalyst tablet using a standard laboratory catalyst tableting machine. Different nozzles are used in the tablet press to make catalyst sheets of different shapes. A batch of ingots was made using the current three-valve die, and another batch of ingots was made using the modified three-valve die.

The side crush strength was measured using the LTCM-6 w/DFM 100 crush strength system of the Chatillon Force System. The average side crush strength (£) of the current three-lobed tablet is £8.1, which is typical for this catalyst formulation and shape. The average side crush strength (£) of the modified three-lobed tablet is £27.8, which is more than three times that of the current three-lobed. As can be seen from this data, there is a surprisingly significant increase in the side crush strength of the modified three-lobed tablet.

Percentage loss was measured for the current three-lobed tablets and the modified three-lobed tablets. Measured using a rotating cylinder with a diameter of 10 inches (254 mm) and a height of 6 inches (152 mm) with a single radial baffle extending the full height of the cylinder by 2 inches (51 mm). The interior of the cylinder has a surface roughness of no greater than about 250 microinches (6.4 μm). Approximately 110 grams of catalyst flakes were gently sieved through a #20 (850 μm) screen. The pre-screened catalyst tablets were transferred to a wide-mouth container and weighed to approximately 0.01 grams. The test cylinder and lid of the device were cleaned using a fine bristle brush. Approximately 100 grams of pre-screened catalyst tablets were weighed to an accuracy of 0.01 grams and recorded as weight "A". The weighed pre-screened catalyst tablets are then transferred to another cylinder, carefully sealed and rotated. The barrel will be rotated 1800 rpm at 60+5 rpm. A #20 (850 μm) screen with a plate attached was placed under the barrel and the lid was carefully removed. Use a fine bristle brush to clean the contents of the tube from the barrel and cover and pour it onto a screen. The fine particles are sieved into the pan by gently shaking the sieve by hand, and excessive agitation should be avoided. In this test, the fine grain scale produced by wear and loss was removed to 0.01 g, and this weight was recorded as "B". The percentage loss of wear is calculated by the following formula:

Loss%=(A-B)/A×100

When the wear rate is less than 1.0%, it should be recorded as "less than 1%". In this test method, the percent wear represents the weight percent of catalyst fines having a diameter of less than about 850 μm produced during the test.

The current three-valve type catalyst has a percentage loss of 14.4%, which is typical for this type of catalyst. The modified three-valve type catalyst has a percentage loss of 9.27%. As can be seen from the data, the modified three-valve has a surprisingly significant percentage loss of about 40%.

Preliminary fill data shows that the modified three-lobed type has a higher catalyst density in the reactor tube than the current three-lobed type. A larger catalyst density improves the loading of the catalyst in each reaction tube.

While the invention and its advantages are described in detail, it is understood that various changes, substitutions and changes may be made herein without departing from the scope of the invention.

Figure 1A illustrates the current three-lobed sheet, a solid cylindrical structure having three void spaces traveling along the height of the cylinder.

Figure 1B illustrates a top view from the current three-lobed tablet.

Figure 1C illustrates a top view of the current three-lobed tablet with its cylindrical radius and lobes radius.

Figure 2 illustrates a top view of the modified three-lobed tablet of the present invention with its cylindrical radius and modified flap radius.

Figure 3A illustrates a partial enlarged top view of the current three-lobed tablet of Figure 1C with a clearer definition of its cylindrical radius and lobes radius.

Figure 3B illustrates a partially enlarged top plan view of the modified three-lobed tablet of Figure 2 with a clearer definition of its cylindrical radius and lobes radius.

Claims (20)

A shaped oxidation catalyst structure for preparing maleic anhydride, characterized in that: (1) comprises a catalytic material composed of a mixed oxide of vanadium and phosphorus; and (2) has a solid cylindrical structure, wherein The cylindrical structure has a cylinder height and a cylindrical radius, and the solid cylindrical structure has three void spaces that travel along the height of the cylinder to form three lobes, wherein each lobes has a corner defined by the lobes radius, wherein the cylinder The ratio of radius to lobes radius is equal to or less than about 15. The shaped oxidizing catalyst structure of claim 1, wherein the ratio of the radius of the cylinder to the radius of the lobes is equal to or less than about 12. The shaped oxide catalyst structure of claim 1 wherein the ratio of the radius of the cylinder to the radius of the valve is equal to or less than about 10. The shaped oxide catalyst structure of claim 1 wherein the ratio of the radius of the cylinder to the radius of the valve is equal to or less than about 8. The shaped oxide catalyst structure of claim 1 wherein the ratio of the radius of the cylinder to the radius of the valve is about 6.25. The shaped oxide catalyst structure of claim 1 wherein the shaped structure has a loss of less than about 10%. The shaped oxide catalyst structure of claim 1 wherein the shaped structure has a side crush strength greater than about 10 pounds. The shaped oxide catalyst structure of claim 1 wherein the shaped structure has a side crush strength greater than about 15 pounds. The shaped oxidation catalyst structure of claim 1, wherein the shaped structure has Side crush strength greater than about 20 pounds. The shaped oxidation catalyst structure of claim 1, wherein the catalytic material is represented by the chemical formula: VP _x O _y M _z ; wherein M is at least one promoter element selected from the group consisting of IA, IB, IIA of the periodic table, a group of elements consisting of Groups IIB, IIIA, IIIB, IVA, IVB, VA, VB, VIB or VIIIB, x being a value between about 0.5 and about 2.0, and y being a V present in the composition in an oxidized state A value chosen for the valence of P, M, and z is a value from 0 to about 1.0. The shaped oxidizing catalyst structure of claim 10, wherein x is a value between about 0.95 and about 1.35 and z is a value of at most about 0.5. The shaped oxidation catalyst structure of claim 10, wherein the M system is selected from the group consisting of elements of Groups IA and IIB of the Periodic Table of the Elements. The shaped oxidation catalyst structure of claim 12, wherein M selected from Group IA is lithium and M selected from Group IIB is zinc. The shaped oxidation catalyst structure of claim 10, wherein the M system is selected from the group consisting of elements of Groups IA and VIIIB of the Periodic Table of the Elements. The shaped oxidation catalyst structure of claim 14, wherein M selected from Group IA is lithium and M selected from Group VIIIB is iron. A method for preparing maleic anhydride, comprising the steps of reacting a hydrocarbon having at least four carbon atoms in a linear chain with a molecular oxygen-containing gas in the presence of a shaped oxidation catalyst structure, the molded structure being characterized by: 1) comprising a catalytic material composed of a mixed oxide of vanadium and phosphorus; and (2) having a solid cylindrical structure, wherein the cylindrical structure has a cylinder height and a cylinder radius, and the solid cylindrical structure has three Along the cylinder The highly advanced void spaces form three lobes, wherein each lobes has a corner defined by the lobes radius, wherein the ratio of the radii of the cylinder to the radii of the lobes is equal to or less than about 15. The method of claim 16, wherein the hydrocarbon is selected from the group consisting of saturated hydrocarbons, unsaturated hydrocarbons, cyclic hydrocarbons, aromatic hydrocarbons, and mixtures thereof. The method of claim 16, wherein the hydrocarbon is selected from the group consisting of n-butane, 1-butene, 2-butene, benzene, and mixtures thereof. The method according to item 16 of the request, wherein the reaction temperature is between about 300 deg.] C to about 600 deg.] C, and at a pressure between the space velocity of between about 100hr ^-1 to about 5000hr ^-1, the negative pressure to super atmospheric pressure. The method of claim 16, wherein the reaction is at a temperature between about 325 ° C and about 450 ° C, a space velocity between about 1000 hr ^-1 and 3000 hr ^-1 , and about 1.013 x 10 ² kPa - gauge to about 3.45 x 10 Performed under pressure between ² kPa and gauge pressure.